Corequisite Support Activity for 2B: Sampling Bias

What you’ll need to know:

In this support activity you’ll become familiar with the following:

  • Apply a statistical definition to the word random.
  • Distinguish between a sample and a population.
  • Distinguish between a statistic and a parameter.

In the next preview assignment and in the next class, you will need to identify the difference between a sample and a population, as well as understand why a random sample is needed to make inferences about a population. Prepare for that in this corequisite support activity by exploring uses of the word random and practicing using the terms sample and population, and statistic and parameter.

The Word Random

Question 1

Choose the best meaning for random in this sentence:

“Sometimes I say random things to my friend.”

  1. a) Haphazard, weird, out of the ordinary
  2. b) Without order or pattern
  3. c) Without prior knowledge, criteria, or method
  4. d) By chance
  5. e) Without bias

Question 2

Discuss the best meaning for random in the following sentence. How is the meaning different than in Question 1?

“A group of participants was selected using a simple random sample for the survey.”

 

The use of the word random in everyday language might be like saying:

”I saw a random person with a cat on his head in New York.”

Black and white photo of a man standing on a sidewalk with a cat sitting on his head.

The word random in statistics is used to describe things like objects pulled from a hat—every object has an equal chance of being selected.

An upside down top hat
Let’s try to discern the uses of the word random one more time. This time, you come up with a sentence that uses random in a non-statistical and a statistical way.

Question 3

3) What is an everyday use of the word random? What image can you think of?

question 4

4) What is another way to think about the use of the word random in statistics? What image can you can think of?

Distinguish between sample/population and statistic/parameter

In What to Know [2A], you learned about populations and samples. You saw that one primary use of statistics is to make inferences about a population based on data collected on a sample from that population. The population is the group of individuals or entities that our research question pertains to (e.g., all Americans), and a parameter is a numerical summary measure that summarizes that population (e.g., the proportion who use social media). A sample is a group of individuals or entities on which we collect data, and a statistic is a numerical summary measure of a sample.

Let’s practice distinguishing between sample and population, statistic and parameter. Use the following scenario to answer Questions 5 – 8.

A survey is administered to undergraduate students at college in Nebraska about their attitudes on the new learning management system used in all courses. Of the 40,322 students enrolled at the college, a random sample of 2,500 students were surveyed.

question 5

5) What is the population in the given scenario?

question 6

6) What is the sample in the given scenario?

question 7

7) What would be an example of a parameter in this context?

question 8

8) What would be an example of a statistic in this context?

In this corequisite support activity, you’ve learned the statistical definition of random, and learned to distinguish between a sample and population and between a statistic (of the sample) and a parameter (of the population). Let’s move on to the course section and activity to practice using these terms!